A judge in the US state of Maryland on Thursday dropped all charges against police officer Caesar Goodson in the death of 25-year-old Freddie Gray last year, including second-degree murder.

Gray suffered a lethal neck injury while in police custody. His death prompted protests and rioting across Baltimore.

Goodson, who drove the van in which Gray was critically injured, also faced charges of manslaughter, assault, misconduct in office and reckless endangerment.

Baltimore Circuit Judge Barry Williams' acquittal of 46-year-old Goodson marks a significant blow to State Attorney Marilyn Mosby's efforts to hold police officers accountable for the death of the young black man.

In May, the same judge acquitted police officer Edward Nero of reckless endangerment and misconduct in office in Gray's death.

Williams also declared a mistrial in December after a jury failed to agree on manslaughter charges for another officer involved in the incident.

Three other officers are expected to stand trial for Gray's death.

Call for calm

State Senator Catherine Pugh, who is the Democratic nominee in Baltimore's mayoral race, issued a statement calling for calm after the verdict.

"Protests are a vital part of democracy, but to destroy the homes and businesses many people have worked very hard to build is unacceptable," Pugh said.

Last year, riots triggered by Gray's death led to looting of shops, forcing Maryland's governor to announce a state of emergency and bring in the National Guard to restore peace.

"It is important to respect each other and to respect our neighborhoods," she added.

ls/jm (AP, Reuters, AFP)